The parents of a South Korean conscript soldier who killed five comrades in a grenade and gun attack pleaded with him to surrender on Sunday, after he exchanged fire with troops who had tracked him down near a school close to the North Korean border.

Late on Saturday night, the soldier threw a grenade and opened fire, killing five members of his unit and wounding seven others, at an outpost in the base at Goseong county, a mountainous region that borders the North on the eastern coast of the peninsula.

A manhunt went in to full swing at daybreak, with helicopters sweeping the heavily forested hillsides and special forces took part in a search that, according to a colonel briefing media, involved the equivalent of nine battalions.

Discovered hiding near a school some 10 kilometres (6 miles) from the base, the soldier opened fire on troops, wounding a platoon leader in the arm, YTN television news channel reported.

The parents of the soldier, according to Yonhap news agency, were taken to the site, where his mother pleaded with him to surrender as a stand-off developed after the initial burst of gunfire.

“I heard several gun shots for 10 minutes,” Byun Sang-man, a 80 year old farmer, told Reuters from the village.

“We can't go outside... Soldiers have spread out all around our town. The headman told people this morning to stay inside through loudspeakers.”

A military official identified the soldier as Sergeant Lim, and said he was due to be discharged on 16 September.

The official, who requested anonymity as they were not authorised to speak to the media, described Lim as an “introvert” and said there had been earlier concerns over his psychological health, but he was deemed fit to be deployed to the outpost after passing a test in November.

Yonhap news agency reported some details of the events at the base on Saturday night.

“He first threw a grenade and then opened fire. He was returning after completing his day shift duty,” Yonhap reported.

Following the shooting the military threw a cordon around the search zone, including guard posts along the Demilitarized Zone, a 2.5-mile wide swathe of land serving as a buffer between the two Koreas since the end of the 1950-53 Korean War.

North and South Korea are technically still at war as their conflict ended in a truce, not a peace treaty and the border is regarded as potentially one of the world's most dangerous flashpoints.

The shooting comes at a sensitive period for South Korea, with the nation still in shock after the death of more than 300 people, mostly school children, in a ferry disaster in April.

The defense ministry issued an apology to the nation over the shooting. The military has been criticised over similar incidents in the past.

The military has been criticized before for lax discipline in some units and failure to prevent previous cases where soldiers, suffering personal problems, have shot fellow soldiers.

In a similar incident in 2011, a South Korean marine went on a shooting spree at a base near the tense maritime border with North Korea, killing four fellow soldiers before trying to blow himself up with a hand grenade.

All able-bodied South Korean men must serve about two years under a conscription system, and there are concerns that the new recruits are softer and find it harder than past generations to adapt to military life.